Recently, electronic devices such as personal computers and smartphones are equipped with functions of wireless communications and wireless power transmission. In electronic devices, for broadening distance of wireless communication, better efficiency, and a smaller size, a soft magnetic film for concentration of magnetic flux is disposed around an antenna or coil included in the electronic device (for example, see Patent Document 1).
Patent Document 1 discloses a flexible magnetic film formed by blending a flat soft magnetic powder with a binder.
Meanwhile, for improvement in efficiency of magnetic flux concentration, it is important to improve magnetic properties such as relative magnetic permeability (in particular, real part μ′ of complex magnetic permeability). Generally, increasing the thickness of the magnetic film improves the shielding effect of the magnetic field. However, because a thin magnetic film and furthermore, a small-sized electronic device are demanded, it is difficult to meet the demand of a thinner thickness with the above-described method.
Thus, a method in which the content ratio of soft magnetic particles in a magnetic film is increased has been known (high filling) (for example, see Patent Document 2).
Patent Document 2 discloses an electromagnetic interference suppressor obtained by dispersing the soft magnetic powder to which a surface treatment is given by using a surface treatment agent containing Si elements in a binder.